Abstract: A method produces a connection interface in a tubular filter element for filtering liquids, including a filter mat (10). The opposite ends (14) of the filter mat are interconnected in a connection position by a planar weld seam (28) provided with an embossed strip in the region of the free ends (14) of the filter mat. A region is provided between the embossed weld seam (30) and the beginning of the transition towards the tubular filter mats, in which a smooth weld seam (32) is applied without embossing in a flat strip along the ends (14) of the filter mat. This arrangement enables the ends of the filter mat to be welded together in a strong and long-lasting manner. The embossed weld seam is simultaneously unloaded of any stress by the smooth weld seam.

Abstract: A method of assembling a filter element includes the initial step of forming a plastic filter casing with openings from a flat blank with opposite ends thereof bent towards one another and joining these opposite ends together by a sealing seam. Also, a resilient mat filter is folded into a cylindrical shape and pushed open on a fluid-permeable supporting pipe to surround and engage the surrounding pipe. The cylindrical shape of the mat filter has an exterior diameter prior to introduction into the casing that is larger than an interior diameter of the filter casing along the entire axial length of the mat filter. The mat folder is folded into a conical shape to facilitate its introduction thereof into the filter casing. After the axial end is formed, the mat filter and supporting pipe are introduced into the filter casing to define a filter chamber. Finally, two end caps are joined to the filter casing.

Abstract: The invention relates to a method for producing a connection interface in a tubular filter element for filtering liquids, comprising a filter mat (10), the opposite ends (14) of said filter mat being interconnected in a connection position by means of a plane weld seam (28) which is provided with an impressed strip in the region of the free ends (14) of the filter mat. A region is provided between the impressed weld seam (30) formed in such a way and the beginning of the transition towards the tubular filter mats, in which a smooth weld seam (32) is applied without impression in a flat strip along the ends (14) of the filter mat. This enables the ends of the filter mat to be welded together in a strong and long-lasting manner, the impressed weld seam being simultaneously unloaded of any stress by means of the smooth weld seam. The invention also relates to a device for carrying out the method.